The present invention relates generally to a closure casing, and particularly to a closure casing for enclosing one or more elongate objects such as pipes or cables, which latter term will be understood hereinafter to include both electrically conductive cables and optical cables comprising bundles of optical fibres.
Optical fibres are increasingly used in telecommunications systems and a number of techniques have been developed for joining such fibres at particular points within a communications network. Likewise, electrically conductive cables or wires have to be joined at certain places within the network and at all such junctions closure casings are required in order both to support the connection and to provide protection against environmental agencies such as moisture and dust.
Optical fibres may be joined in a number of ways, utilizing techniques such as splicing or devices such as couplers or splitters. A common feature of all such connections, however, is the requirement for a closure casing which has means for allowing ingress of one or a plurality of cables or bundles of fibres at one end and for egress of one or more cables or bundles of fibres at the other. Such closure casings also find particularly utility where it is necessary to install equipment at an intermediate point along a transmission line. Such equipment may, for example, include repeaters, amplifiers, boosters, attenuators or other such equipment (which equipment is mentioned by way of example and is not intended to be an exhaustive list nor to prejudice the generality of the invention) but whatever equipment the closure casing encloses the common features nevertheless remain that the casing must be capable of being sealed against environmental agencies and have sufficient strength and rigidity to resist external forces and protect the, sometimes delicate, components enclosed therein. Such closure casings in use may be buried underground, or housed in cabinets or other locations in the network.
Although such closure casings must be capable of sealing securely against environmental agents it is very often necessary to gain access to the interior of the casing (so-called xe2x80x9cre-entryxe2x80x9d requirement) in order to make changes to the network or for maintenance purposes in the event of a failure or breakdown. This re-entry requirement means that a closure casing has to be fastened with releasable fasteners of one form or another and cannot be permanently secured such as by adhesive or welding of the components unless it is acceptable for the casing to be disposed of, upon re-entry, and replaced with a fresh casing. Economically, in view of the complexity of the structure, this is usually not viable.
The present invention seeks to provide a closure casing having releasable fasteners for securing the casing parts in the closed condition, and to a fastener for such a closure, which is releasable quickly and easily to allow an operator access to the interior of the closure casing.
One way in which this has been done in the prior art, is to provide the casing with a surrounding ring or clamp which is held in its closure position by an overcentre clamp or toggle latch. WO96/33922 illustrates such a casing. Closure casings in which co-operating parts are held together by toggle clamps are also shown in EP 0 546 267 which describes a clamping closure for closing a cable sleeve having a clamping claw engageable over a flange at the rim of the closure, and U.S. Pat. No. 4,558,174 which describes a closure for a cable splice having mating covers held closed by a continuous wire latch support frame having a plurality of latching fingers which can snap past a centered bistable position into locking engagement with an aligned seat along the closure. A disadvantage with such structures lies in the relatively complex shape of the outside of the closure casing resulting from the presence of the over-centre clamps which makes the casing difficult to handle and requires extra space for it to be housed. Independent over-centre clamps (also known as toggle clamp) are, of course, known as such. One example is described in U.S. Pat. No. 4,367,569, in which it is referred to as a cam locking pin. This has a pivoted pawl at one end, which can be turned to a first position allowing it to be passed through aligned openings in two components to be held together, and a second position in which it resists removal of the pin from the openings. At its opposite end the pin has aligned transverse lugs engageable by a force-applying tool having a pair of hooks removably engageable with the lugs and having respective wedging portions by which tension can be applied to the pin to hold the components together. Disadvantages of this device include the requirement for manual dexterity in manipulating the pivoted pawl, and the fact that this and its associated pivot pin increase the number of components parts of the device and therefor the cost of construction and assembly, as well as the risk of malfunction due to components being out of tolerance.
As used herein the term xe2x80x9ctoggle clampxe2x80x9d will be understood to relate to a mechanism comprising two parts pivotally engaged or engageable with respect to one another, one of which comprises a tension member and the other of which comprises an operating member or lever. The axis about which the two parts of the clamp are turnable with respect to one another is spaced from an effective point of contact between the operating member or lever and a part of the closure which it engages in use, the arrangement being such that in turning about the pivot axis between the two clamp members from a release position to a clamped position the line of action through the contact point with the closure member is displaced transversely of the line of action between the pivotable connection between the two clamp members and the contact point of the tension member with the other closure member, passing through a xe2x80x9ccentrexe2x80x9d position in which the pivot axis and the said two lines of action are all aligned, at which point the tension applied to the tension member is at its greatest. In the closure position, therefore, the tension applied to the tension member holds the operating lever in its closed position.
The resilience in a toggle clamp mechanism is usually provided by making the tension member of such a material and shape that it can be stressed upon the application of a tensile force between each end or by the provision of a separate spring of the toggle clamp mechanism acting between the tension member and the operating member or lever such that the spring is compressed as the operating lever moves towards its point of maximum compression as the two lines of action are aligned.
U.S. Pat. No. 4,727,629 discloses a fastener for removably clamping the edges of two panels, each having a hole therethrough. The fastener includes a hinge pin, about which the fastener body pivots.
FR 2,199,363 discloses a toggle clamp for clamping a plate to a support or to another plate. There is no suggestion to use this clamp for closure casings.
GB 599,354 discloses a pin for temporarily securing together sheet metal plates. The pin proper has two legs which can be forced together by a pivotable body member to permit insertion of the pin in holes. The legs can move apart to clamp the plates together.
U.S. Pat. No. 5,524,672 discloses a pipe thread protector having a toroidal body of elastomer with a bore to accept a pipe end and a metal band and a toggle clamp arrangement extending around its periphery.
According to one aspect the present invention provides a closure casing having two co-operating closure members comprising half-shell structures having cable entry ports and defining an enclosed space between them when in a juxtaposed closure position, the closure being provided with holding means for holding the closure members together in the closure position characterised in that the holding means comprises at least one over-centre or toggle clamp. mechanism one part of which passes through openings in the closure members which are aligned when the closure members are in the said closure position, and engages a face of the closure member remote from the other part of the toggle clamp mechanism, which other part is turnable between a clamped position in which tension is applied to the said one part, and a release position.
By passing one of the parts of the toggle clamp mechanism through aligned openings in the closure members it is possible to obtain a number of important benefits. First, unlike conventional toggle clamp mechanisms, the operating lever, and possibly also the tension member, need not project beyond the general outline of the closure casing. This, therefore, makes the outline of the closure casing much less irregular, and protects the operating lever of the toggle clamp mechanism from disturbance or damage by contact with adjacent parts.
Another important advantage lies in the possibility of orientating the toggle clamp mechanism such that the axis about which the two toggle clamp parts are pivotally connected need no longer necessarily be parallel to the closure line between the two closure casing members as has been necessary in the past. Indeed, it is a separate aspect of the present invention to provide a closure casing having two co-operating closure members defining an enclosed space between them when in a juxtaposed closure position, in which there is provided a toggle clamp mechanism having two relatively turnable parts which can be turned in relation to one another about an axis generally transverse the meeting line of the co-operating members of the closure casing.
In a preferred embodiment there may be a plurality of toggle clamps along an extended meeting line between two casing members which may be formed as two half-shells fitting together about co-operating respective perimetral rims.
In a preferred embodiment of the invention at least one of the closure members has a resilient element engageable by a part of the said toggle clamp mechanism and operable to apply a resilient resistance to the clamping movement thereof to hold the clamp in its locking position when moved thereto against the resistance exerted by the resilient element.
Such resilient element may be a laminar resilient strip overlying a surface portion of the casing.
In embodiments of the invention in which the said closure members are co-operating half shells they may be provided with respective flanges around perimetral rims thereof which are brought together when the casing is closed, and in such an embodiment the said resilient element may comprise a strip or stringer lying along the length of at least one flange on one of the casing members.
In such arrangement the flange provided with the resilient strip may have a cavity therein adjacent the opening through which passes the said one part of the toggle clamp mechanism and across which the said resilient strip spans. Alternatively, of course, the resilient strip need not be rectilinear, but provided with an arcuate portion which is stressed towards a rectilinear configuration by the forces applied by the toggle clamp upon closure.
Preferably the said one part of the toggle clamp mechanism has a transverse projection for engaging the face of the closure member remote from the other part of the toggle clamp mechanism. The said transverse projection may be in the form of two oppositely directed substantially symmetrical projections for engaging opposite sides of an opening in the said closure member, or may be in the form of a single hook for engaging one side of a said opening.
In the case of a closure casing having a clam shell configuration in which the two co-operating casing members are half-shells these may have a generally elongate form to define two opposite ends for entry and exit of cables or bundles of optical fibres, and in this case there may be a plurality of toggle clamp mechanisms spaced around at least part of the perimeter of the closure members.
In a preferred embodiment of the present invention the said other part of the toggle clamp mechanism comprises a body portion having two parallel sides with respective aligned openings or cavities for receiving respective pivot pins of the said one member such that the said one member is located, in use, between the said two parallel sides, and an operating tab or lever which projects from the body portion and lies substantially parallel to the surface of the co-operating closure member when the clamp is in its locking position.
Such a configuration allows the clamp to be manipulated manually, without requiring special tools, and this can be further encouraged by the provision on the said body portion of the said other part of the latch mechanism of a face extending generally transversely of the operating tab or lever. This may serve as a release member against which, in use, a force may be applied to release the clamp from its locking position. Of course, in embodiments in which there are a plurality of such clamps, the force applied by each clamp is a fraction of the overall closure force, and this facilitates manual manipulation of the clamps avoiding the requirement for a manipulating tool which may be needed if only a single clamp is provided.
A closure casing according to the invention may further be provided with a sealing member located inwardly of the clamp or clamps for sealing the interior volume of the casing when closed.
According to another aspect of the present invention a closure casing having two co-operating closure members defining an enclosed space between them when in a juxtaposed closure position is provided with closure means in the form of at least one toggle clamp mechanism comprising two relatively turnable parts which can be moved in relation to one another between an over-centre clamping or locking position in which the two parts apply a closing pressure to the two co-operating closure members, and a release position, and in which at least one of the closure members carries a resilient element which is stressed by the toggle clamp mechanism when the parts thereof are in the clamping position whereby to apply a resisting force to maintain the parts of the toggle clamp in their over-centre position and the two closure members pressed against one another.
The present invention also comprehends a toggle clamp mechanism as such, and according to a further aspect of the present invention an over-centre or toggle clamp mechanism for holding together two co-operating members of a closure casing comprises two clamp parts which are pivotally interengaged or interengageable, one clamp part being adapted to pass through aligned openings in the said two co-operating closure members and engage the closure member remote from the other clamp part, the said one clamp part being a unitary member having at least one transverse projection for engagement with the said remote closure member.
The said one clamp part may be turnable about an axis parallel to its length whereby to turn the transverse projection between engagement and release positions with respect to the said remote closure member.
The closure casing of the present invention may be provided with means to resist the release of the or each toggle clamp mechanism.
The means to resist the release of the or each toggle clamp may act to resist movement of the or each toggle clamp from its clamped to its release position.
Alternatively or additionally the means to resist the release of the or each toggle clamp may act to resist the withdrawal of the said one part of the or each toggle clamp through the openings in the closure members.
The means to resist release of the or each toggle clamp may comprise at least one aperture in a part of the toggle clamp mechanism engageable by cooperating removable obstruction means.
Following insertion of the toggle clamp through the openings of the closure members the apertures may receive said removable obstruction means, which may include R-clips, tie wraps, locking wire or padlocks which will provide different levels of security depending on the security requirements.
In another embodiment of the invention at least one of the closure members has a resilient element engageable by a part of the said toggle clamp mechanism and operable to apply a resilient resistance to the clamping movement thereof whereby to hold the clamp in its locking position when moved thereto against the resistance exerted by the resilient element, the said at least one resilient element being relatively displaceable with respect to the adjacent closure member so as to reduce the effective dimensions of the openings, through which a member of the toggle clamp passes whereby to obstruct withdrawal thereof.
When a toggle clamp tension member with an enlarged end is passed through the openings the resilient element can be moved so as to reduce the effective dimensions of the openings to the extent that the enlarged head cannot pass back therethrough. This is very useful in practice to prevent individual toggle clamps becoming dislodged from the casing prior to final securement.
The use of narrow elongate openings with flat hooks is advantageous in securing toggle clamps in a closure member flange of minimum width around the closure without the openings unacceptably weakening the flange.
The resilient element may be retained in a channel formed by at least a part of the closure member, so as to allow longitudinal movement thereof.
The said channel may include at least a part which is not rectilinear so as to apply stress to the resilient element when the channel and resilient element are in a juxtaposed position.
In a preferred embodiment the resilient element is associated with a lower flange and is relatively displaceable therefrom. The relative displacement may be achieved, for example, by the provision of a channel formed by the lower flange. Alternatively or additionally the resilient element may be held in place adjacent the lower flange by the use of fixing means, for example screws or the like and the openings used to accept the screws in the resilient element are elongate such as to allow a degree of movement of the resilient element with respect to the fixing means. Other means for allowing relative displacement of a resilient element with respect to a flange such as magnetic interaction are also not beyond the scope of the invention.
In a further embodiment of the invention the toggle clamp mechanism may have means for engagement by a tool whereby to assist in operating the mechanism.
The said means for engagement by a tool may comprise at least one cavity in the said toggle clamp mechanism.